1. Field of the Invention
The present invention relates generally to a current consumption controlling apparatus and method of a dual-mode portable terminal, and, in particular, to an apparatus and method for reducing current consumption when transmit burst times of two transceivers overlap each other.
2. Description of the Related Art
A conventional portable terminal which supports a plurality of communication systems operates in only one communication mode, and not simultaneously in two communication modes, through the handoff from a mode which supports one communication system to a mode which supports another communication system. However, a recent portable terminal is required to operate in two communication modes which support different communication systems and to support the handoff between the different communication systems; that is, the vertical handoff.
Typically, a portable terminal adopting a Time Division Duplex (TDD) scheme consumes a relatively high amount of current at a specific moment. For example, when a transceiver of the portable terminal adopting the TDD scheme transmits one frame, the current consumption abruptly increases during a transmit burst time, as shown in FIG. 1A.
When the portable terminal supports two communication modes at the same time, the instant in which the greatest current consumption occurs of the TDD based portable terminal in the transmit burst time may cause a problem. In particular, when the two communication modes of the portable terminal operate at the same time and their two transceivers enter the transmit burst time, the current consumed by the transceivers is likely to increase in a moment. For example, when a TDD based portable terminal, which supports a Global System for Mobile communication (GSM) network and a Wireless Broadband (WiBro) network, operates in the GSM mode, considerable current is consumed during the GSM transmit burst time, as shown in FIG. 1A. When the portable terminal operates in the WiBro mode, considerable current is consumed during the WiBro transmit burst time, as shown in FIG. 1B. In this situation, when the TDD based portable terminal supports the GSM network and the WiBro network at the same time and accordingly the transmit burst times of the two transceivers overlap each other, all of the current consumptions of the respective modes simultaneously occurs. As a result, the excessive current consumption is caused, as shown in FIG. 1C. As such, the amount of the current excessively consumed by the two transceivers in an instant exceeds the capability of the portable terminal, to thus deteriorate the stability and the reliability of the portable terminal.